Color filter arrays for area image sensors, such as CCD, CID, and MOS devices for dyed filter elements are formed by coating photopatternable layers, imagewise exposing, washing off unexposed layer portions, and then dyeing the remainder filter layer by dye imbibition.
In one approach, hydrophilic colloids, for example, gelatin, can be suspended in water along with a radiation responsive hardening (i.e., cross-linking) agent to form the photopatternable composition. The hydrophilic colloid can be employed in combination with a dichromate salt employed as the radiation responsive hardening agent.
In another approach, diazo resins are the photoresponsive polymers for forming the photopatternable composition. The diazo resin can be mixed with a mordant to produce a photopatternable composition employed to form the dyed filter elements. A variety of mordants are known which are compatible with the formation of photopatternable layers by the diazo resin. These approaches are described in European Patent Application No. 249,991.
However, these and other approaches have not been entirely satisfactory for a variety of reasons. It is difficult to produce dyed filter elements having good rheological properties, speed, high resolution, sharp edge profiles, and uniform dye density. Another major problem is the fading of dyed filter elements resulting from prolonged exposure to light, heat and humidity. Also, effective green filters using dyed layers are difficult to produce.